1. Field of the Invention
The present invention relates generally to a magnetic tape cassette in which a front lid is pivotably mounted on the cassette housing so as to selectively open or close a front opening portion for a tape path of the cassette housing in order to protect a magnetic tape from being damaged. More particularly, this invention relates to a magnetic tape cassette of the sort as described above which is suitable for accommodating therein a magnetic tape on and/or from which a PCM (pulse-code-modulated) signal is recorded and/or reproduced.
2. Description of the Prior Art
FIGS. 1 and 2 are illustrations, respectively, of a conventional magnetic tape cassette in which a magnetic tape for a PCM signal is accommodated.
As FIG. 1 shows, a cassette housing 1 is comprised of an upper section or half la and a lower section or half lb, which are secured together by suitable conventional means such as screws. A pair of reel hubs 2a and 2b are mounted rotatably in the cassette housing 1, and a magnetic tape 3 is wound on the pair of reel hubs 2a and 2b. A front lid 4 is pivotably mounted on the cassette housing 1 so as to selectively open or close the front opening portion of the cassette housing 1.
Now, FIG. 1 shows the state in which the front opening portion of the cassette housing 1 is closed by the front lid 4. The front lid 4 comprises a lid main section 4a and a pair of side supporting sections 4b. The lid main section 4a has a rectangular configuration having a length and width sufficient so that it can close the entire front opening portion of the tape cassette. The pair of side supporting sections 4b are elongated from both side ends of the lid main section 4a and bent backwards at a right angle. The side supporting sections 4b respectively each have a shaft aperture which is rotatably supported by a shaft 6 formed at a predetermined position on each side wall of the cassette housing. The front lid 4 is made of a plastic material having sufficient flexibility or elasticity so that when it is warped toward the cassette housing 1 side, it can be engaged with the front opening portion of the cassette housing 1 due to its elastic deformation, thus being halted at a predetermined position to close the front opening portion of the cassette housing 1.
FIG. 2 illustrates the conventional magnetic tape cassette of this example which is ready for recording or reproduction. As FIG. 2 shows under this condition, the front lid 4 is opened manually or automatically by automatic lid opening and/or closing mechanisms (not shown) of a tape recorder or the like and the magnetic tape 3 is exposed in the front opening portion of the cassette housing 1.
As described above, the magnetic tape cassette of this example is provided with the front lid 4 so that without a specially-prepared cassette case, upon non-use, as illustrated in Fig. 1, the front opening portion of the cassette housing 1 is closed by the front lid 4 so as to protect the magnetic tape 3 in the front opening portion from being touched by fingers or the like. Also, by the front lid 4, dust, smudges and the like can be prevented from entering the main body of the magnetic tape cassette.
In the thus arranged magnetic tape cassette, the front lid 4 can be rotated symmetrically in an up and down direction relative to the front opening portion of the cassette housing 1, thus making it possible to independently effect the recording and/or reproduction on both tracks A and B of the magnetic tape 3. When accommodating a plurality of such tape cassettes into a cassette magazine in such a fashion that the tracks A and B of each tape cassette are aligned side by side, they have to be put into the cassette magazine with their tracks A and B aligned while looking at the indications of label areas on the tape cassettes.
Meanwhile, a so-called micro-tape cassette is known and it is the smallest tape cassette now available on the market. If such a micro-tape cassette is further miniaturized, for example, to be substantially 25.times.20.times.5 mm in size, the track indication on the label area becomes difficult to see. Hence, such very small magnetic tape cassettes are difficult to be accommodated within a cassette magazine so as to align their tracks A and B side by side.
When the magnetic tape 3 provided within the cassette housing 1 is transported at a constant speed, with the lid 4 opened, a capstan rotatably contacts with a guide roller (not shown) provided within the cassette housing 1 and at the side wall portion adjacent to the front opening or tape path portion of the tape cassette for transport therebetween. Under this condition, since the front lid 4 is located at the surface side of the cassette housing 1, or above the front opening portion of the cassette housing 1, the front lid 4 opposes or contacts the bearing of the capstan or a capstan arm, though not shown. To solve this problem, the capstan has to be formed long in length. If the length of the capstan is increased, the capstan occupies a larger space in its location and this causes the apparatus such as a tape recorder to inevitably become large in size.